No, they can't.

Emphasis mine:

Swarm Subtype: A swarm is a collection of Fine, Diminutive, or Tiny creatures that acts as a single creature.

First, while a swarm may act as a single creature, it isn't one. Second, you wouldn't Wild Shape into either a Small or Medium creature.

So, per the rules as written, you cannot Wild Shape into a swarm.

However, like you said, it can be a bit open to interpretation. You should consult your GM to see if they'd allow this. I probably would, depending on what kind of swarm.

The key word in the rake description is "typically." So rake says

A creature with this special attack gains extra natural attacks under certain conditions, typically when it grapples its foe.

It then goes on to tell you how the ability works under the typical conditions:

In addition to the options available to all grapplers, a monster with the rake ability gains two free claw attacks that it can use only against a grappled foe. The bonus and damage caused by these attacks is included in the creature’s description.

Finally, there is a limitation placed on using the rake ability in these typical conditions:

A monster with the rake ability must begin its turn already grappling to use its rake—it can’t begin a grapple and rake in the same turn.

But then we have pounce, which grants a specific exception:

When a creature with this special attack makes a charge, it can make a full attack (including rake attacks if the creature also has the rake ability).

Specific trumps general, so the extra attacks from a rake can be used when pouncing.